Fluorosurfactants which incorporate betaine groups are known for use as additives in fire extinguishing compositions. The betaine group allows such fluorosurfactants to undergo electrostatic interactions with other components in a fire fighting composition therefore improving performance.
In U.S. Pat. No. 4,383,929, Bertocchio et al. disclose fluorinated sulfobetaine compounds and methods for their production. These fluorinated sulfobetaines are prepared by alkylation of a fluorianted amine with either a) sultone propane in chloroform or b) a chlorosulfonic salt in water or ethanol. The aqueous processes disclosed in Bertocchio et al. typically have high chloride contents from around 8 to 16 weight percent. To reduce the chloride content, Bertocchio et al. teach dissolving the dried fluorinated sulfobetaines in highly flammable absolute ethanol, where the metal chloride salts can then be filtered out, distilling the ethanol, and redissolving the solid fluorinated sulfobetaine in water.
The known aqueous processes to produce fluorinated sulfobetaines produce a final product that is high in free chloride. High chloride presents a problem in promoting corrosion in metal storage containers. Current attempts to reduce chloride levels are focused around removal of ethanol and water by distillation to obtain dry fluorinated sulfobetaine, redissolving it in absolute ethanol, filtration of the metal chlorides, followed by distillation of the ethanol and isolation of solid sulfobetaine. While these additional steps reduce the final chloride levels, they are tedious and require large amounts of ethanol, a filtration apparatus, a distillation, and handling powdery or solid products.
Alternatively, to reduce the chloride content, fluorinated sulfobetaines are prepared in flammable organic solvents. The resulting compositions are highly flammable and require removal of flammable organic solvents by distillations to increase the flash point prior to transportation.
A process that results in reduced chlorides without the need to add highly flammable ethanol followed by a distillation of ethanol would not only reduce the cost of production, but also reduce ethanol usage is needed. A process that also results in a stable homogeneous solution of product with a high flash point would allow for transporting the fluorinated sulfobetaines prior to when the final fire fighting foam formulation is needed. The present invention meets these needs of providing a process that produces a a solution of low chloride, high flash point fluorinated sulfobetaine product.